Clinical features and outcome of mixed connective tissue disease in developmental age – observational study from one center

OBJECTIVES: Mixed connective tissue disease is a rare systemic connective tissue disease of developmental age and it includes the features of arthritis, polymyositis/dermatomyositis, systemic lupus erythematosus and systemic sclerosis, with presence of anti-ribonucleoprotein antibodies (anti-RNP) in serum. Early diagnosis of the disease is difficult but essential in preventing development of systemic complications, which are often irreversible. International literature does not report many studies on large cohorts of children with this disease. The aim of this retrospective study was to define clinical characteristics and long-term results of treatment of the disease in 60 children with mixed connective tissue disease hospitalized in the period between 1978 and 2018. The diagnosis was established on the basis of Kasukawa’s criteria. MATERIAL AND METHODS: It was a group of 60 children (46 girls and 16 boys) aged 10.5 on average (4–16.5). When assessing general symptoms at the onset of the disease according to Kasukawa’s criteria, the highest number, over 80% of children, demonstrated symptoms suggesting SLE, about 40% suggesting DM and about 25% suggesting SSC. In the period of observation the number of children with clinical symptoms suggesting SSC increased. The most common clinical symptoms included Raynaud syndrome, arthritis and myositis and the most common irregularities in the test results included presence of anti-RNP antibodies and rheumatoid factor and hematological symptoms such as leukopenia/thrombocytopenia. Restrictive lung function impairment was demonstrated by 20% of children. Treatment most often included combined therapy (glucocorticosteroids + methotrexate/azathioprine). RESULTS: In 70% of the patients stable improvement was observed. Remission concerned 7% of the patients, frequent exacerbations were found in almost 20% of patients, and 2 children (3.5%) died. CONCLUSIONS: The long term observations of patients in developementeal age with mixed connective tissue disease revealed that the majority of them had domination of SLE symptoms, only in 7% achieved remission and 70% remained in stable improvement. Serious infections with septic state were the cause of death in two cases.